This invention relates to bearings and, more particularly, bearing assemblies having bearings arranged in serial fashion.
The use of anti-friction bearings is well-known. Such bearings permit free relative motion between different parts of a machine. The bearings may hold or guide moving machine parts, while simultaneously minimizing energy-wasteful friction. Additionally, the bearings minimize wear on the machine parts, which wear may change the dimensions of the machine parts rendering them useless.
The operation of bearings are limited by at least two factors. Specifically, the working specification for a high load, high speed bearing is usually specified by the product of the maximum total load P times the maximum speed V. For a bearing with a given PV value, one can increase the working speed under a reduced load and, likewise, one can increase the load under a reduced speed. However, in either case of reducing the speed or the load, certain maximum limits of speed and load also apply.
When a bearing is used in a particularly high speed or high load application, special materials and constructions have often been used in order to minimize the possibility of failure of the bearing. However, such special materials, extra high quality tolerance levels, or other special constructions are often quite costly. Further, special arrangements or constructions are often complex, difficult to assemble, and subject to other disadvantages. For a bearing assembly having a single bearing mechanism, binding or jamming of the bearing mechanism results in complete failure of the bearing assembly.
In order to deal with high speed bearing requirements, various compound bearing arrangements have been developed. Such bearing arrangements use at least two sets of bearings, each set bearing between two different surfaces.
The following U.S. patents are illustrative of bearing designs including a plurality of sets of bearings:
______________________________________ U.S. Pat. No. Inventor Issue Date ______________________________________ 1,366,966 Spear Feb. 1, 1921 1,433,014 Kennedy Oct. 24, 1922 1,494,695 McCluskey May 20, 1924 1,506,856 McCluskey Sep. 2, 1924 1,748,174 Hirvonen Feb. 25, 1930 1,742,841 Witthofft Jan. 7, 1930 1,798,529 Foley Mar. 31, 1931 2,647,807 Brunstrum Aug. 4, 1953 3,452,349 Wood Jun. 24, 1969 3,597,029 Marcum Aug. 3, 1971 4,045,100 Beauchet Aug. 30, 1977 ______________________________________
The Spear patent shows a roller conveyor wherein the rollers are mounted upon a ball-bearing assembly having a plurality of ball bearings radially spaced and disposed upon opposite sides of a member.
The Kennedy patent shows a compound bearing assembly having two sets of ball bearings at opposite ends of a front axe of an automobie. Each set of ball bearings is axially and radially spaced from an adjacent set of ball bearings. An alternate compound bearing uses ball bearings which are radially spaced, but in a common plane.
The McCluskey '695 patent shows a bearing arrangement using a plurality of radially spaced roller bearings disposed in a common plane.
The McCluskey '856 patent shows a radial serial bearing having ball inlets to facilitate insertion of ball bearings in the assembly.
The Hirvonen patent shows a compound bearing arrangement for a spindle. Gears and eccentrics are used to minimize wear.
The Witthofft patent discloses a bearing arrangement having a plurality of radially spaced balls in a concentric arrangement and having a radially movable locking member to lock the ball bearings in position.
The Foley patent shows a roller bearing having a plurality of gears which are adapted to cause an intermediate ring to move in a direction opposite to the rotation of shaft. As shown in FIG. 3, gear teeth are located on a plurality of annular members.
The Brunstrum patent shows a bearing arrangement using a plurality of concentrically arranged ball bearings and having a structure such that one set of bearings is used when the shaft is turning in one direction and the other set of bearings is used when the shaft is turning in the opposite direction.
The Wood patent shows a plurality of concentrically arranged ball bearings. The arrangement includes a mechanism whereby one set of the ball bearings is held in reserve and only used upon failure of the other set of ball bearings.
The Marcum patent discloses a planetary bearing assembly wherein a plurality of radially spaced bearings are used for high speed installations.
The Beauchet patent discloses a concentric anti-friction bearing assembly wherein bearing elements running in races of different diameters are disposed approximately in the same radial plane.
Additionally, the French patent 1,284,704 of Gatserelia issued on July 4, 1962 shows different arrangements in which various pluralities of ball bearings are radially offset in concentric planes and/or disposed in parallel planes. As shown in FIG. 2, three sets of bearings may be arranged concentrically in a common plane with three additional sets of bearings arranged concentrically in another plane axially offset from the first plane.
Although the above and other bearing designs have been generally useful at minimizing friction, they have been subject to numerous disadvantages. In particular, the cost, ease of construction, and operational characteristics have often been less than desirable. Further, they have generally lacked the ability to consistently distribute speed between various of the machine parts. Without any arrangement to accurately and consistently distribute speed or relative motion throughout several of the machine parts, the limit of maximum speed for such bearing assemblies has been lower than desirable.